...After a few months of 2.0 4/4 ownership I have found myself contemplating swapping for a nice new 3 wheeler. ...
What's this - a rational question regarding an irrational purchase decision?

Have to say I never contemplated a M4W but fell for the M3W when they came out. For 2-up touring the M4W might be easier / more comfortable, but you could say the same about touring in a Caterham.